#include <stdio.h>
#include <iostream>
using namespace std;

int main(){
    int s;
    cin>>s;
    if(s>=90)
        cout<<"A";
    else if(s<=89 && s>=80)
        cout<<"B";
    else if(s<=79 && s>=70)
        cout<<"C";
    else if(s<=69 && s>=60)
        cout<<"D";
    else
        cout<<"E";
    return 0;
    }